It’s unknown whether Tom Joyce will survive as head of embattled Knight Capital, which has attracted two bids. Photo: Bloomberg

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A bidding war for Knight Capital is heating up.

The broker-dealer that was on the brink of extinction four months ago is slated to get a second offer — this one from Virtu Financial — today or tomorrow, sources familiar with the situation told The Post.

A Virtu offer to purchase the Wall Street trading firm run by CEO Tom Joyce would come as a rival offer from Getco Holding Co. — said to be a $3.50-a-share cash and stock bid — values Knight at roughly $1 billion.